Rajat Saxena

I’m pleased to share our new paper, “Hippocampal ripple diversity organizes neuronal reactivation dynamics in the offline brain”, out in @cp-neuron.bsky.social !

With @vitorlds.bsky.social and David Dupret, we show that diversity in ripple current profiles shapes reactivation dynamics

Ultra-high-density Neuropixels probes improve detection and identification in neuronal recordings To understand the neural basis of behavior, it is essential to sensitively and accurately measure neural activity at single-neuron and single-spike re…

Neuropixels Ultra!

By @steinmetzneuro.bsky.social, who led a big collaboration

www.sciencedirect.com/science/arti...

This is really exciting work! Congratulations!!

1/8
How can the brain create countless unique memories using a single, universal metric of space? We’ve been waiting for the answer to this for two decades!
Read it here:
www.biorxiv.org/content/10.1...

Functional independence of entorhinal grid cell modules enables remapping in hippocampal place cells A systems-level understanding of cortical computation requires insight into how neural codes are transformed across distinct brain circuits. In the mammalian cortex, one of the few systems where such ...

1/5 How does the brain turn the low-dimensional, universal grid cell metric into the rich, diverse codes needed for memory in hippocampal place cells? 🧵
Preprint link 👇

www.biorxiv.org/content/10.1...

1/
🚨 New preprint! 🚨

Excited and proud (& a little nervous 😅) to share our latest work on the importance of #theta-timescale spiking during #locomotion in #learning. If you care about how organisms learn, buckle up. 🧵👇

📄 www.biorxiv.org/content/10.1...
💻 code + data 🔗 below 🤩

#neuroskyence

Coherent dynamics of thalamic head-direction neurons irrespective of input While the thalamus is known to relay and modulate sensory signals to the cortex, whether it also participates in active computation and intrinsic signal generation remains unresolved. The anterodorsal...

🚨New preprint alert!

The thalamus has long been seen as a relay of sensory signals to cortex.
But could it also generate its own structured activity?
Our study explores this question in the head-direction (HD) system.

Some explanation 🧵👇 1/13

www.biorxiv.org/content/10.1...

Thrilled to share that our work is now published in Science! ✨

We found a preference for visual objects in the mouse spatial navigation system where they dynamically refine head-direction coding. In short, objects boost our inner compass! 🧭

www.science.org/doi/10.1126/...

🧵1/

Check our new preprint where we examine how enriched experiences alter synaptic connectivity and coding sparsity across the neocortex.

Congratulations Roxana! I hope you had a fun celebration

This is a super interesting paper from Bruce McNaughton’s lab, showing why we should study behavior in the context of natural/ecological environments. They show that living in enriched complex environments, prior to task performance, affects both behavior and the underlying neural activity.

Representational drift without synaptic plasticity Neural computations support stable behavior despite relying on many dynamically changing biological processes. One such process is representational drift (RD), in which neurons' responses change over ...

When neurons change, but behavior doesn’t: Excitability changes driving representational drift

New preprint of work with Christian Machens: www.biorxiv.org/content/10.1...

Variations in neuronal selectivity create efficient representational geometries for perception Our visual capabilities depend on neural response properties in visual areas of our brains. Neurons exhibit a wide variety of selective response properties, but the reasons for this diversity are unkn...

In many brain areas, neuronal tuning is heterogeneous. But how does this diversity help behavior? We show how tuning diversity shapes representational geometry and boosts coding efficiency for perception in our new preprint: www.biorxiv.org/content/10.1...
(w/ @sueyeonchung.bsky.social&Tony Movshon)

A new study led by @timothysit.bsky.social reveals that different layers of mouse V1 integrate visual and non-visual signals differently.

Activity is dominated by vision (or spontaneous fluctuations) in L2/3 and by movement in L5. This leads to different geometries.
www.biorxiv.org/content/10.1...

I'm pleased to share our new work, “Spatio-temporal organization of network activity patterns in the hippocampus”, out in @cp-cellreports.bsky.social !
With Demi Brizee & David Dupret, we track how oscillations and spiking behaviour map onto hippocampal layers using an LFP-based embedding.

(1/13)

Congratulations! 🎉

Direct entorhinal control of CA1 temporal coding Nature Communications - Temporal coding in the hippocampus is thought to be key for memory and predictions. Here, the authors show that blocking one entorhinal input affects two aspects of...

Our collaboration - from PhD work - examining input-specific (EC L3) contributions to rate and temporal coding in CA1 place cells is now out in @natcomms.nature.com 🔬🧠

rdcu.be/evWtz

Dopamine encodes deep network teaching signals for individual learning trajectories Longitudinal tracking of long-term learning behavior and striatal dopamine reveals that dopamine teaching signals shape individually diverse yet systematic learning trajectories, captured mathematical...

Super excited to see this paper from Armin Lak & colleagues out! (I've seen @saxelab.bsky.social present it before.)

www.cell.com/cell/fulltex...

tl;dr: The learning trajectories that individual mice take correspond to different saddle points in a deep net's loss landscape.

🧠📈 🧪 #NeuroAI

Our study is out in Nature!
Using wireless Neuropixels we recorded hippocampal activity in freely flying bats and uncovered replay and theta(less) sweeps, revealing striking differences from classic rodent models.

👉 www.nature.com/articles/s41...

Power Pixels: a turnkey pipeline for processing of Neuropixel recordings There are many open-source tools available for the processing of neuronal data acquired using Neuropixels probes. Each of these tools, focuses on a part of the process from raw data to single neuron a...

Do you do Neuropixel recordings and are you struggling with preprocessing? The Power Pixels pipeline is an easy-to-use pipeline from raw data to neural activity of single neurons in specified brain regions 🧠 Now on bioRxiv!
www.biorxiv.org/content/10.1...

We observed that hippocampal SWRs arriving near the Down-to-Up or Up-to-Down transitions of the sleep slow oscillations (SO) can entrain novel memory replay in cortex, while the middle phase of the Up state tends to replay familiar cortical memories.

Our work with Maxim Bazhenov's group showing interleaved replay of new and old memories within individual Up states using a combination of biophysical modeling and electrophysiology experiments.

Event structure sculpts neural population dynamics in the lateral entorhinal cortex Our experience of the world is a continuous stream of events that must be segmented and organized at multiple timescales. The neural mechanisms underlying this process remain unknown. In this work, we...

Your brain doesn’t just passively track time ⏳ - it structures it.
In @Science.org we show that activity in 🧠 memory circuits (LEC) drifts constantly, but makes sharp jumps at key moments, segmenting life into meaningful events. (1/2)

👉 www.science.org/doi/10.1126/...

Our new paper out now in Science explores how neural activity in the lateral entorhinal cortex (LEC) *drifts* over time - and *jumps* at key boundaries - to help organize events in memory.

🔗 www.science.org/doi/10.1126/...

Here's a quick summary of what we found 🧵👇

Your brain learns for you even when you're not actively learning. Maybe. (in mice).

Wassifier/MergedClassifier.ipynb at master · rajatsaxena/Wassifier spike sorting cluster classifier. Contribute to rajatsaxena/Wassifier development by creating an account on GitHub.

Thanks for compiling the list. At some point, Marius and I were working on building ML models combining spatio-temporal waveform profile and autocorrelogram for unit classification as good/mua vs noise. Never finished integrating it into the KS pipeline

github.com/rajatsaxena/...

Kilosort4 detects a LOT of neurons, I recorded 15k neurons in one year 🤯 Traditionally, one would curate these detected units to see if they are well isolated single neurons. This is not feasible anymore, so today let's look at three options that are out there to automate this process! 🤖👇

I Fell Asleep While Driving, Which Led to This Diagnosis This health condition is often overlooked in women.

Over the past few years, I’ve shared my personal journey as a sleep scientist living with sleep apnea with other scientists and students to raise awareness and reduce stigma. I’m excited to reach an even broader audience in my recent interview with Parade 🎉

parade.com/health/i-fel...

The Hippocampus Book Abstract. The Hippocampus Book investigates the structure, function and pathology of the hippocampus and related cortical areas. It highlights the importan

As I transition over to Bluesky I have to plug our new #book. If you haven't already, check out the 2nd edition of The #Hippocampus Book!

academic.oup.com/book/59509?s...

Awake replay: off the clock but on the job Hippocampal replay is widely thought to support two key cognitive functions: online decision-making and offline memory consolidation. In this review, we take a closer look at the hypothesized link bet...

New opinion paper in @cp-trendsneuro.bsky.social with Dan Bendor, where we argue that rodent studies provide only marginal support for the idea that replay supports real-time decisions (e.g. planning). Fictive learning and memory tagging are more consistent w/evidence. www.cell.com/trends/neuro...